16,255 research outputs found
Topological susceptibility in Lattice QCD with unimproved Wilson fermions
We address a long standing problem regarding topology in lattice simulations
of QCD with unimproved Wilson fermions. Earlier attempt with unimproved Wilson
fermions at \beta =5.6 to verify the suppression of topological susceptibility
with decreasing quark mass (m_q) was unable to unambiguously confirm the
suppression. We carry out systematic calculations for two degenerate flavours
at two different lattice spacings (\beta = 5.6 and 5.8). The effects of quark
mass, lattice volume and the lattice spacing on the spanning of different
topological sectors are presented. We unambiguously demonstrate the suppression
of the topological susceptibility with decreasing quark mass, expected from
chiral Ward identity and chiral perturbation theory.Comment: 1 figure and clarifying remarks added, results and conclusion
unchanged. Accepted for publication in Physics Letters
Non-local space-time supersymmetry on the lattice
We show that several well-known one-dimensional quantum systems possess a
hidden nonlocal supersymmetry. The simplest example is the open XXZ spin chain
with \Delta=-1/2. We use the supersymmetry to place lower bounds on the ground
state energy with various boundary conditions. For an odd number of sites in
the periodic chain, and with a particular boundary magnetic field in the open
chain, we can derive the ground state energy exactly. The supersymmetry thus
explains why it is possible to solve the Bethe equations for the ground state
in these cases. We also show that a similar space-time supersymmetry holds for
the t-J model at its integrable ferromagnetic point, where the space-time
supersymmetry and the Hamiltonian it yields coexist with a global u(1|2) graded
Lie algebra symmetry. Possible generalizations to other algebras are discussed.Comment: 12 page
Integrable open-boundary conditions for the supersymmetric t-J model. The quantum group invariant case
We consider integrable open--boundary conditions for the supersymmetric t--J
model commuting with the number operator and . Four families, each
one depending on two arbitrary parameters, are found. We find the relation
between Sklyanin's method of constructing open boundary conditions and the one
for the quantum group invariant case based on Markov traces. The eigenvalue
problem is solved for the new cases by generalizing the Nested Algebraic Bethe
ansatz of the quantum group invariant case (which is obtained as a special
limit). For the quantum group invariant case the Bethe ansatz states are shown
to be highest weights of .Comment: Latex, 24 pages. Some new comments and references. Final version to
appear in Nucl. Phys.
Macro-anatomical variation of the olfactory apparatus in some Indian teleosts with special reference to their ecological habitat
The anatomy of the peripheral olfactory apparatus (i.e. olfactory lamellae, olfactorychambers, accessory nasal sacs, olfactory nerve tracts, olfactory bulbs and brain) of some teleosts, viz. Pseudapocryptes lanceolatus (Bloch and Schneider, 1801) — an air breathing mudskipper, Lepidocephalichthys guntea (Hamilton, 1822) — a freshwater scavenger fish and Mastacembelus armatus (Lacepède, 1800) — a freshwater potamodromous fish, has been studied in relation to their specific ecological habitat. Live, adult, sex-independent fish species were collected from the local markets of West Bengal, India, and acclimatised with the laboratory conditions (for 72 h at 32°C). The specimens were anaesthetised by MS-222 (dose: 100–200 mg/L). Olfactory apparatuses were dissected out and fixed inaqueous Bouin’s solution. The macro- and microstructures (using haematoxylin and eosin) of the olfactory apparatuses were examined under binocular light microscope (LM) and trinocular LM (Primo Star; Carl Zeiss Microscpy, GmbH, Germany) respectively. P. lanceolatus possesses unilamellar olfactory apparatus at therounded snout, whereas L. guntea shows small rosette with 18 to 24 lamellae oneither side of the elliptical snout. Elongated olfactory rosette (number of lamellae ranges from 60 to 76) is present at the pointed snout of M. armatus. Morpho-anatomical variation in snout structure of the respective species is an indicative of divergence in ecological habitat, but variation in olfactory apparatus is significant for species-specific differentiation. Pseudostratified olfactory neuroepithelial components (i.e. sensory receptor cell, supporting cell and basal cell) show striking similarities amongst these species. Therefore comparative anatomical changes of the snout and olfactory apparatus are not only representing ecological habitat based on interspecific variation, but may also indicate the phylogenetic relation amongst said species
Astrophysical and Cosmological Tests of Quantum Theory
We discuss several proposals for astrophysical and cosmological tests of
quantum theory. The tests are motivated by deterministic hidden-variables
theories, and in particular by the view that quantum physics is merely an
effective theory of an equilibrium state. The proposed tests involve searching
for nonequilibrium violations of quantum theory in: primordial inflaton
fluctuations imprinted on the cosmic microwave background, relic cosmological
particles, Hawking radiation, photons with entangled partners inside black
holes, neutrino oscillations, and particles from very distant sources.Comment: 25 pages. Amendment to section 7. Contribution to: "The Quantum
Universe", special issue of Journal of Physics A, dedicated to Prof. G.-C.
Ghirardi on the occasion of his seventieth birthda
Lepto-hadronic interpretation of 2021 RS Ophiuchi nova outburst
Very high energy (VHE; 100 GeV E 100 TeV) and high energy (HE; 100
MeV E 100 GeV) gamma-rays were observed from the symbiotic recurrent
nova RS Ophiuchi (RS Oph) during its outburst in August 2021, by various
observatories such as High Energy Stereoscopic System (H.E.S.S.), Major
Atmospheric Gamma Imaging Cherenkov (MAGIC), and {\it Fermi}-Large Area
Telescope (LAT). The models explored so far tend to favor a hadronic scenario
of particle acceleration over an alternative leptonic scenario. This paper
explores a time-dependent lepto-hadronic scenario to explain the emission from
the RS Oph source region. We have used simultaneous low frequency radio data
observed by various observatories, along with the data provided by H.E.S.S.,
MAGIC, and \textit{Fermi}-LAT, to explain the multi-wavelength (MWL) spectral
energy distributions (SEDs) corresponding to 4 days after the outburst. Our
results show that a lepto-hadronic interpretation of the source not only
explains the observed HE-VHE gamma-ray data but the corresponding model
synchrotron component is also consistent with the first 4 days of low radio
frequency data, indicating the presence of non-thermal radio emission at the
initial stage of nova outburst. We have also calculated the expected neutrino
flux from the source region and discussed the possibility of detecting
neutrinos.Comment: 18 pages, 5 figures, 2 tables; accepted for publication in The
Astrophysical Journal (ApJ
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